"Written in the History books: Words that changed my life for the best."

This phrase suggests that there were certain words or a message that had a profound impact on the speaker's life, leading to positive changes. It implies that these words were significant enough to be recorded in history books, indicating their lasting importance. The speaker seems to attribute their personal growth and transformation to these words, highlighting the power of language and communication in shaping one's life journey. Overall, the phrase conveys a sense of reflection, gratitude, and perhaps even inspiration derived from the impact of certain words on the speaker's life.